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RightingBot landing ability inspired by lizards

By Damir Beciri

30 June 2012

Inspired by lizards, which have the ability to turn right side up and land on their feet when they fall, the researchers from the University of California, Berkeley, developed a robot able to mimic that ability. Named RightingBot, the lizard-inspired robot mimics lizards which swing their large tails one way to rotate their body the right way before they hit the ground.

Lizards in their natural environment encounter various situations where they could fall. For instance, they could fall while fighting over territory, seeking food, or even mating. To avoid injuries, they must have a way to turn themselves during a fall to land safely on their feet.

“It is not immediately obvious which mechanism an animal will use to accomplish aerial righting and recover from falling in an upside-down posture. Depending on body size, morphology and mass distribution there are multiple strategies for animals to execute this behavior,” said Ardian Jusufi, lead author of the study.

The researchers used high-speed videography to analyze the motion of two common lizards – the flat-tailed house gecko and green anole – as they fall, starting upside down. Gathered information revealed that both lizards swing their tails in one direction to right themselves in mid-air before landing on extended legs.

The team also compared the righting movement of the two lizards, which have similar body sizes but different tail lengths and inertial properties. The results led to discovery that the gecko with a shorter tail has to swing its tail further to the side to right itself, making a larger angle relative to its body. The gecko with a two times longer tail needed smaller movements to reorient its body.

Berkeley researchers developed a three-dimensional mathematical model to test their understanding of the lizards’ righting movement. In order to try those mathematical model’s predictions, the team built the RightingBot – simple robot consisting out of a body joined to a tail.

RightingBot is able to right itself in mid-air with a swing of its tail in a way inspired by the lizards, showing how useful a tail can be for that purpose. Unlike other researches where the tail is inspired by cats or monkeys who use them in a different way, this research could lead to simpler air- or land-based robots able to right themselves while falling or after a collision.

The study was recently presented at the Society for Experimental Biology meeting on 29th June in Salzburg, Austria.